NCCER Electrical Level 3 Module 5 Overcurrent Protection Practice Test

To determine the full-load current rating of a 225 kVA, three-phase transformer operating at 240V, you apply the formula for calculating the full-load current in a three-phase system, which is:

\[ \text{Full-load current} (I) = \frac{\text{kVA} \times 1000}{\sqrt{3} \times \text{Voltage (V)}} \]

In this case, the kVA rating of the transformer is 225, and the operating voltage is 240V. Plugging in the values, the calculation becomes:

\[ I = \frac{225 \times 1000}{\sqrt{3} \times 240} \]

Calculating the square root of 3 gives approximately 1.732, so we follow through with the calculation:

\[ I = \frac{225000}{1.732 \times 240} \]

Calculating the denominator:

\[ 1.732 \times 240 = 415.68 \]

Therefore:

\[ I = \frac{225000}{415.68} \]

Solving this results in:

\[ I \approx 541.82 \text{A} \]

Rounding this to the nearest whole